WASHINGTON — In politics, it is sometimes better to be lucky than good. Republicans and Democrats, and groups sympathetic to each, spend millions on sophisticated technology to gain an advantage.

They do it to exploit vulnerabilities and to make their own information secure. But sometimes, a simple coding mistake can lay bare documents and data that were supposed to be concealed from the prying eyes of the public.

Such an error by the Republican Governors Association recently resulted in the disclosure of exactly the kind of information that political committees given tax-exempt status usually keep secret, namely their corporate donors and the size of their checks. That set off something of an online search war between the association and a Washington watchdog group that spilled other documents, Democratic and Republican, into the open.

The documents, many of which the Republican officials have since removed from their website, showed that many of America’s most prominent companies, from Aetna to Walmart, had poured millions of dollars into the campaigns of Republican governors since 2008. One document listed 17 corporate “members” of the governors association’s secretive 501(c)(4), the Republican Governors Public Policy Committee, which is allowed to shield its supporters from the public.

“This is a classic example of how corporations are trying to use secret money, hidden from the American people, to buy influence, and how the governors association is selling it,” said Fred Wertheimer, the president of Democracy 21, a nonpartisan group that advocates more transparency and controls over political money.

The trove of documents, discovered by watchdogs at the Democrat-aligned Citizens for Responsibility and Ethics in Washington, or CREW, sheds light on the secretive world of 501(c)(4) political groups, just as the battle over their future intensifies. Unlike the Republican Governors Association, the tax-exempt Republican Governors Public Policy Committee is not required to disclose anything, even as donors hit the links, rub shoulders and trade policy talk with governors and their top staff members.

At a policy committee symposium last year at the Omni La Costa Resort and Spa in Carlsbad, Calif., committee members included the health insurers Aetna and WellPoint, the insurance lobby America’s Health Insurance Plans, the utility giant Southern Company, and the lobbying firms Dutko Grayling (now known as Grayling), BGR Group and Leavitt Partners.

With Congress producing so little legislation, governors’ offices have become attractive targets, Mr. Wertheimer said. Last year, the Republican Governors Public Policy Committee allowed corporate donors to make their cases on how to carry out the Affordable Care Act; discuss hydraulic fracturing, an oil- and gas-exploration method regulated at the state level; and hash over state budgets just as coffers began to loosen.

The spokeswoman for the governors association, Gail Gitcho, said the organization did not reveal the names of donors to its tax-exempt arm, and she denounced CREW as a group of partisan hypocrites who refused to divulge their own donors as they unmasked others. CREW has for years maintained that it is nonpartisan, but last month, it was taken over by David Brock, a former conservative who now runs a network of groups aligned with Democrats.

“CREW accessed those documents from behind a password-protected website,” Ms. Gitcho said. “CREW hides behind the facade of an educational group when their only real purpose is to act as a liberal front group for Democrats.”

In a tit for tat, the Republican association unearthed documents from the Democratic Governors Association that also name corporate donors and the benefits: meetings with Democratic governors, “preferred seating” at policy discussions, and lavish receptions. But those documents do not detail contribution levels, nor do they reveal the corporate members of the Democratic association’s own secretive 501(c)(4), the Center for Innovative Policy.

Among the R.G.A. documents is a 21-page schedule of the policy committee’s Carlsbad meeting last year that lists which companies attended, who represented them and what they contributed. The most elite group, known as the Statesmen, whose members donated $250,000, included Aetna; Coca-Cola; Exxon Mobil; Koch Companies Public Sector, the lobbying arm of the highly political Koch Industries; Microsoft; Pfizer; UnitedHealth Group; and Walmart. The $100,000 Cabinet level included Aflac, Blue Cross Blue Shield, Comcast, Hewlett-Packard, Novartis, Shell Oil, Verizon Communications and Walgreen.

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Gov. Bobby Jindal of Louisiana was at a 2011 donor event.CreditMike Theiler/Reuters

Other documents detail, in part, what they received in return.

One 2009 document states the benefits of a Governors Board membership, for a $50,000 annual contribution or a one-time donation of $100,000, saying it “offers the ability to bring their particular expertise to the political process while helping to support the Republican agenda.”

Board members received two tickets to “an exclusive breakfast with the Republican governors and members of their staff”; three tickets to the Governors Forums Series, where “a group of 5-8 governors discuss the best policy practices from around the country on a particular topic”; and a D.C. Discussion Breakfast Series, among other events.

If they bump up to Cabinet Membership — $100,000 annually or a single payment of $200,000 — contributors also receive two invitations to “an exclusive Gubernatorial Dinner,” an “intimate gathering with the Republican governors and special Republican V.I.P. guests” at the Willard InterContinental Hotel in Washington.

Political finance experts say the practice apparently laid out in the documents is not illegal, and probably not unusual. In hundreds of pages posted online, the Republican governors group put it down in black and white.

“It’s not that you don’t suspect this, but here you see these companies paying the governors for access,” said Melanie Sloan, the executive director of CREW. “Americans all think it’s pay-to-play politics. This is what confirms it.”

Donors refused to comment on their membership in the 501(c)(4). But those who would speak more broadly said they had also given to Democrats. Cynthia Michener, a spokeswoman for Aetna, pointed to the company’s public political contributions disclosure, which showed gifts of $300,000 each to the Republican and Democratic governors associations last year. It lists nothing to the two groups’ tax-exempt arms.

The R.G.A. documents, dating to 2008, show just how well the governors’ corporate contributors have been treated. Gov. Gary R. Herbert of Utah and the Mississippi governor at the time, Haley Barbour, hosted donors in 2010 at the St. Regis Deer Valley Resort in Park City, Utah, for an event featuring skiing and snowmobiling. At the association’s 2012 annual conference in Las Vegas, donors not only received access to the governors, staff and “V.I.P. guests,” but were also treated to an “under the Eiffel Tower” event at the Paris Las Vegas hotel’s Chateau Nightclub, taken clay shooting and offered a “back of house” tour at Wynn Las Vegas.

Of course, the perks came with a cost. Hotel room drops, the gifts welcoming attendees to Las Vegas, ran to $7,500 per sponsor. One donor was sought to sponsor wireless Internet in the meeting spaces for $25,000.

The governors association’s 2011 annual conference in Orlando included a welcoming reception at Universal Studios’ Wizarding World of Harry Potter, a golf swing clinic, afternoons at SeaWorld and Disney World, and a late-night party hosted by the lobbying firms Blank Rome Government Relations and Dutko Grayling.

Also in 2011, the Republican governors Rick Perry of Texas, Bobby Jindal of Louisiana and Bob McDonnell of Virginia gathered donors at the Newseum and the W Hotel, among other Washington sites, for dinners, senior staff briefings and an invitation-only breakfast.

This month, Mr. McDonnell, whose term ended in January, was convicted of public corruption charges for accepting hundreds of thousands of dollars in cash, loans and gifts from a donor. During the trial, Mr. McDonnell’s tenure leading the Republican Governors Association came up often as a window into the group’s high-stakes fund-raising.

Tax documents filed this year show that the R.G.A. raised $27 million last year, much of it from declared corporate donors such as Chrysler, Archer Daniels Midland, Altria and Genworth Financial.

The list of members of the tax-exempt arm of the governors association attending the Carlsbad symposium included three executives from Dutko Grayling, David Beightol, Mary Kay Hogan and Steve Palmer; Loren Monroe of BGR Group and his wife; three executives from WellPoint and Anthem Blue Cross, including Michael Prosio, who was a top aide to Arnold Schwarzenegger when he was the governor of California; and the utility representatives Stoney Burke, the chief lobbyist at Southern Company, and Brad Viator, the director of external affairs at the Edison Electric Institute.

Many of the names of the R.G.A.’s corporate donors would be expected: Allen Richardson, a government affairs manager at Koch Companies Public Sector; Randy Kozuch and Erika Scheffer, political affairs executives at the National Rifle Association; Bill Miller, the chief lobbyist at the Business Roundtable, which represents the chief executives of the largest companies; and Bill Guidera, the senior vice president of Rupert Murdoch’s News Corporation. Maria Cino, a longtime Republican political operative and former official in George W. Bush’s administration, was there representing Hewlett-Packard.

A version of this article appears in print on , on Page A15 of the New York edition with the headline: G.O.P. Error Reveals Donors and the Price of Access. Order Reprints | Today’s Paper | Subscribe